“Tell me something I don’t already know,” says Gordon Gekko in ‘Wall Street’. I’m rather like that when choosing a novel. I used to like science fiction because it was not us/here/now, and dislike kitchen sink dramas for the same reason. I know what it’s like to struggle in a grim northern town, I don’t want to read about it.

Sci-fi and fantasy is escapism and we don’t learn many facts from it, unless very hardcore. One of the appeals of Tolkien is that you can research his world, learn Quenya and the lists of kings but ultimately the whole thing is made up. Movies and TV drama have a difficult relationship with facts, given they need to telescope timelines and adapt the story to whatever budget/set/costumes are available. It is dangerous to come away from something even as well made as ‘I Claudius’ thinking you are secure in the information you have absorbed.

Historical fiction is a great learning tool – or as a writer, it is a teaching tool. For this reason, the facts need to be right and as much of the background must also be populated with truth. If I trust Patrick O’Brian I will learn a great deal about the Royal Navy in the Napoleonic Wars. Thrillers work in a much more us/here/now world which has both advantages and disadvantages. Much prior knowledge of the world can be assumed (readers know what the CIA is and are familiar with the concept of televisions) but there is a parallel danger in that those well-educated readers will also have detailed knowledge of much else. There is still scope for learning, however. I learned a lot about the Sahara as a young man reading Desmond Bagley’s ‘Flyaway’. Getting the facts right helps the suspension of disbelief. We allow the characters to survive deadly scrapes and fall into plots with unlikely regularity in part because everything else around them is so real.

I strained credulity very little in writing Glint of Light on Broken Glass. Our three young people inhabit a very real island in 1913 and are pulled along by the riptide of history. Yes there is a magic-realist element, but I hope I’m forgiven for it given that everything else is solid and grounded. I also hope that readers will learn something they don’t know – something to take away about Guernsey in days gone by and its critically threatened language.

Writers can also make things up with such authority that they are taken as real. John Le Carre famously invented a whole vocabulary for MI6, ‘moles’ and so forth, in such a convincing way that we have come to believe it. When lecturing, I’m aware that I only need to know 5% more than my audience about the given subject to be the expert in the room. I applied this thinking to the Jeffrey Flint books, all of which touched on obscure areas of archaeology or history. However as a writer my audience is potentially the whole world, not 70 people on a rainy Tuesday evening. One reader will be an expert in Soviet rifles, third century Roman armour or actually live in that obscure Greek town where your story is set. So the writer must strain an extra muscle to shrink our own spheres of ignorance to the point we can gloss over the bits it is not necessary to know.

With luck, the reader will come away from the novel thinking “I never knew that…”